In sports racket frames, holes for passing strings through the frame are drilled in the frame and the string is protected from the sharp edges of the holes by a grommet for each hole. The grommet is made of plastic, having a flared end which admits the string into the interior of the frame, and a stem of constant diameter which leads the string and exits the same to the string network area. The grommets are connected at the flared end by a common strip and the assembly is called a grommet strip. For a grommet strip used in the nose region, called a guard strip, its center is recessed so that the string is protected from scratching and its lateral sides are widened to be about the width of the frame so that the nose region is protected from damage if the racket hits the ground during the play.
In the prior art, the conventional bumper/grommet strip arrangement, as described in U.S. Pat. No. 4,204,681, grommets formed in a grommet strip extend into holes formed in a racket frame and grommets formed on a bumper strip extend into holes formed in the grommet strip. There is no provision for permitting the sidewise displacement of any of the grommets to match up with its associated hole in the event of their misalignment.
In U.S. Pat. No. 4,776,592, there is described an exteriorly mounted member having tubular sleeves adapted to be inserted into string holes formed in a racket frame. There is no provision for overcoming the situation wherein one or more of the tubular sleeves are misaligned relative to the string holes. Another arrangement for supporting stringing grommets in a sports racket is disclosed in U.S. Pat. No. 4,496,152. In this arrangement, individual grommets are pressed into holes formed in the racket frame, thereby eliminating the use of a grommet strip altogether.
There are two problems associated with the prior art. One problem is that the center-to-center distance between the grommets in a strip cannot be precisely the same as the distance between the corresponding holes in the frame. This discrepancy often causes considerable difficulty in the stringing of the frame. The guard strip is difficult to stretch to make up for the mismatch between the holes and the grommets because of its stiffness. The smoothness in having the guard strip inserted into the frame with relative ease is a measure of the quality of the molding of the guard strip and the drill jig of the frame. However, it is a costly demand of workmanship.
The second problem is damping of the frame head involving the guard strip. A convenient location for a damping layer is at the interface between the frame and the guard strip. However, since the grommets lodged the guard strip firmly against the recess in the frame preventing it from any axial lengthwise movement between neighboring grommets, the damping layer imbeded between the strip and the surface of the frame will have to move together with the frame as a thick beam during vibration. This prevented any damping effect the damping layer might have contributed to the suppression of the vibration of the frame. The present invention of a new strip improves on that as will be discussed below.
The present extensible grommet strip has the grommets partially isolated in the strip which allows the individual grommets to move relatively easily toward each other so that when the frame holes are not aligned exactly, the grommets can accommodate the mismatch without difficulty.